Ecophysological and genetic traits of the Baltic clam Macoma balthica in the Baltic: differences between populations in the Gdansk Bay due to acclimatization or genetic adaptation?
Hummel, H.; Sokolowski, A.; Bogaards, R.; Wolowicz, M. (2000). Ecophysological and genetic traits of the Baltic clam Macoma balthica in the Baltic: differences between populations in the Gdansk Bay due to acclimatization or genetic adaptation? Int. Rev. Hydrobiol. 85(5-6): 621-637
In: International Review of Hydrobiology. Wiley: Weinheim. ISSN 1434-2944; e-ISSN 1522-2632
Normal and irregular blunt clam-shells were found. Blunt shells increased with depth, because ofincreasing anoxia. Minimal weight-indices and reproductive stages were found at 40 m depth (near thermo-haline stratification) probably due to spawning just before sampling. Clams from shallower stationswere more ripe and heavier due to higher temperatures and re-development than at deeper stations sincetemperatures were still below threshold levels for spawning (10 °C). Respiration was at ambienttemperatures acclimated to standard rates. Consequently, clams from deeper stations (with lower ambienttemperatures) had 2 times higher respiration at the same test-temperature. Clams from the most shallowstation (Puck Lagoon 5 m) showed the worst performance due to adverse hydrodynamics (stagnatedwater, anoxia). Heterozygotes showed better performance than homozygotes (heterosis). In 1995 geneticdifferentiation was found (Idh was diagnostic): clams below 30 m resembled Atlantic populations; shallowstations formed a distinct group (Baltic race). In later years all populations were Atlantic, probablydue to inflow of North Sea water. Before 1996 ecophysiological differences between clams in the GdanskBay can possibly be related to genetic differentiation (adaptations of Atlantic vs. Baltic types), in lateryears differences were due to acclimation to ambient temperatures, salinity and oxygen levels.